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mx.microsoft.com 1; spf=pass smtp.mailfrom=citrix.com; dmarc=pass action=none header.from=citrix.com; dkim=pass header.d=citrix.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=citrix.onmicrosoft.com; s=selector2-citrix-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=vD5+6S7g5mH2XywkXQZuyOwCvE48NX2okNQE1cctsxY=; b=m386p22YELbCmRz3oesAV1oOayGwGcdvWWCQXiQ8WEVBhnmHP65bwLGNPlHWTVZ/UtG3qIZYundrLobauyATGlK1QrOT8S7T7IbN4ckv3voZZrVZy//pifQb9InAtfZG16Zc87ju+HcSQsXG5oWfW8BRrdgi+T3ZAI7DwnN8d0g= To: Jan Beulich , Olaf Hering CC: Ian Jackson , Wei Liu , Xen-devel References: <20210702190342.31319-1-andrew.cooper3@citrix.com> <06968742-355f-ad37-0681-e51eea256414@suse.com> <20210705100228.4947ed4e.olaf@aepfle.de> <20210705103224.26f3835d.olaf@aepfle.de> <1e2a3967-06e5-75ec-3aa5-1f39b6700e63@suse.com> <20210705112548.22ae6d20.olaf@aepfle.de> <5e4986ad-d3ec-18af-b1ea-ccbce57a70ff@suse.com> From: Andrew Cooper Subject: Re: [PATCH] tools/libxenguest: Fix migration's debug option Message-ID: Date: Mon, 5 Jul 2021 11:06:43 +0100 User-Agent: Mozilla/5.0 (X11; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?Windows-1252?Q?M4ygjH277D/R5Ce4gMaomhJWmRSP/EFPW2txTVTmH2kTM6SizzTWpbf/?= =?Windows-1252?Q?ZzR8+Pa2Oek2eAE+cKKhNcha0u/CBbZNxRiYZUH0+rEAeFWJtmtYonFT?= =?Windows-1252?Q?flmpuSYPNpeA6GBySZDMlId29vGnLipIes7wpkXctlCj8beBpZZMEUk6?= =?Windows-1252?Q?YsvWqVlOpDPmvducZgPBriaPT31fKHHweKNR3R4iHrs8lqesiJWg8xpO?= =?Windows-1252?Q?HCfRhyZxtEqGxOpP3UZX1mIAv4NZHuMF4K+UJJ0iR2xgrAKFMJ5Z8+8+?= =?Windows-1252?Q?cXFPtzlFOGwlu1al5EypH4EZJivs7Ygj+IrlYAJsT8KB0BT/vxnxgWzb?= =?Windows-1252?Q?U0TMxLBVvf9RVTWqJM1LMmptq1+e+bJirogrNHH9WPEudeahKr1F+wpF?= =?Windows-1252?Q?LswlVxFsHJWIhrgSRcUfGN/krJoNneiKacCu+7Gjke19vDf4gXUZs/sR?= =?Windows-1252?Q?k8ZZ2zyQFt/JK0q4PJX/kibuLRHSWDokr77MnmxUptlbcd/ul8/hBo6O?= =?Windows-1252?Q?pqIVYtryTSbrstPxNlXopLASxHpfv7PYbU4sbkdwIOVSLKPE1wY45GV7?= =?Windows-1252?Q?zhikuobjQOaSbxLP78+6VaFzSTFW+PuUIBcCpDEE4h8av7BSLNUyF6qC?= =?Windows-1252?Q?ZuDW4FxNAiTWsaQEH+GOzVJIBvaEDKgl5kZFAWVhGmmuQGv54Zbc2P/h?= =?Windows-1252?Q?SKtSQqzhZ0fOCh13OFituGEFaBywM2PP7H/nhcmRL8YPeQ1EtxZS0YEu?= =?Windows-1252?Q?/wLcJJtb+kxbZiI1DrPn+Z5ZUc/h5uPOkDADyAmruLCECp9qgDgR49KA?= =?Windows-1252?Q?LpPfHuyxlQ9eGN4YF6om7IZXhTHMt/aQhkj6WNTkLdgJXVBBfIcB5Fcc?= =?Windows-1252?Q?aHhZUWDTbWnGT3afvcJyeTwGF3zUXT4ig1tJx+otaQsXjZJiLFdtDoMI?= =?Windows-1252?Q?Bk2Jpw2E8pAuHqrj97UkZkRL5q2GQbvwBYaZMWfBtHMfOvE8KTTcURpJ?= =?Windows-1252?Q?0M/0N65zlC83mbR/CEfNaztkGDLGQfp8wMaD45PxhSrigxRa/debuYNr?= =?Windows-1252?Q?7Kht1/FJidHFmtVCfb/vMyQvzA9sb6KrlSuPOtvt4OX0EHzGdiIf90hh?= =?Windows-1252?Q?K3sE1lPj5fvr+B8pqF+wwg81xnZ2DcwnUk7HhSXmPdgGPxv0f/iBjHs2?= =?Windows-1252?Q?pzLyODU5MY3DepBi9Cl5W+rHaTj10oQXNFMFJkPDwe4BYnU2ygcDCptt?= =?Windows-1252?Q?cSqruudRs1pmQ3MzuACZQlY+4j+ZHnhejYrbwCL0QJeeaNhdzfqL588g?= =?Windows-1252?Q?flB96SO0mYK1vLUUFLPcI8YHdU5p8EZv15W0spM70O9VIJY+jR383Ty1?= =?Windows-1252?Q?PSFUMwyifyprbngUa1FrrrfSu5TJOQzgyCklYFVSNqNJiUdq2xgzaWja?= X-MS-Exchange-CrossTenant-Network-Message-Id: 063d4c7c-3093-42b6-a338-08d93f9c9da8 X-MS-Exchange-CrossTenant-AuthSource: BYAPR03MB3623.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 Jul 2021 10:06:54.3327 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 335836de-42ef-43a2-b145-348c2ee9ca5b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: BPNq34/7jiz8T4FZimfmhBxYoLslPBKTFFWikqtYANUbmamnVAyhv43IjTr3fqXhS7XtzoeqEJXh3jH5pt43kO0GuCt2dYnNnydxt9XRJC4= X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR03MB4245 X-OriginatorOrg: citrix.com On 05/07/2021 10:31, Jan Beulich wrote: > On 05.07.2021 11:25, Olaf Hering wrote: >> Am Mon, 5 Jul 2021 11:19:59 +0200 >> schrieb Jan Beulich : >> >>> "The interface" being which one? The tool stack can map the guest's >>> grant table, so it is in the position to find out about all grants >>> without further hypervisor help. >> The interface means the code behind verify_frames. >> >> If there are indeed ways to query which pages belong to grants, how woul= d the toolstack need to do that? > Map the grant table of the guest and walk it, recording any MFN for > which at least one valid r/w grant exists. That doesn't help - Its still racy with in-flight IO.=A0 Also with updates from Xen such as the wallclocks. The only way to fix the IO problem is to disconnect the blk/net rings before doing the final sweep for frames, but that clobbers any ability to restart the VM on the source side if things go wrong at the destination. I don't have an answer at all for the vcpu info frames. ~Andrew